From the Fangio/Staley coaching tree which was the new hot thing on defense at the time.

His time coordinating a winless team was too intriguing to pass up

https://www.acmepackingcompany.com/2021/2/8/22272891/joe-barry-packers-dc-appears-to-be-a-good-example-of-the-nfls-rampant-nepotism-problem

He needed a job. He falling on hard times man.